The Blood and its Circulation 



'39 



V 209. Why the Clotting of Blood is of Vital Importance. 



This clotting of the blood is of vital importance. But for 

 this, a very small cut might cause bleeding sufficient to 

 empty the blood vessels, and death would speedily follow. 

 In slight cuts, Nature plugs up the 

 wound with clots of blood, and thus B -] 

 prevents excessive bleeding. 



Experiment 60. Put two or three drops of 

 fresh blood on a white individual butter plate 

 inverted in a saucer in which is a little water. 

 Cover it with an inverted goblet. Take off 

 the cover in five minutes, and the drop has set 

 into a jelly-like mass. Take it off in half an 

 hour, and a little clot will be seen in the watery 

 serum. 



D 



FIG. 68. Diagram of 

 Clot with Buffy Coat. 



A, serum ; 5, cupped up- 

 per surface of clot ; C, 

 white corpuscles in up- 

 per layer of clot; D, 

 lower portion of clot 

 with red corpusdes. 



Experiment 61. To show the blood clot. 

 Carry to the slaughter house a clean six or 

 eight ounce wide-mouthed bottle. Fill it with fresh blood. Carry 

 it home with great care, and let it stand over night. The next day 

 the clot will be seen floating in the nearly colorless serum. 



Experiment 62. Obtain a pint of fresh blood ; put it into a bowl 

 and whip it briskly for five minutes with a bunch of dry twigs. Fine 

 white threads of fibrin collect on the twigs, the blood remaining fluid. 

 This is "whipped," or defibrinated blood, which has lost the power 

 of coagulating spontaneously. 



NOTE. Fresh blood may be prevented from clotting by adding 

 to it one-fourth part of a saturated solution of Epsom salt and keep- 

 ing it in a cool place. By adding ten times its amount of water, the 

 " salted " blood may be made to clot. 



V 210. The Apparatus for the Circulation of the Blood. 



The apparatus for the circulation of the blood consists of 

 the heart, the arteries, the capillaries, and the veins. 

 The central pump is the heart. 



